This invention relates to dental compositions having viscosities capable of responding to a change in temperature. The invention also relates to methods of applying the composition directly onto a target area of the substrate.
In the dental art, the use of a dental coating composition is generally desirable for a wide variety of applications, such as etching or bleaching. To attain proper application at the desired location, it is desirable that the composition be controllable and slow to flow away from the target site. Thus a high viscosity dental composition in the oral environment would be quite useful.
Currently available dental compositions are provided in seemingly extreme viscosity states. That is, there exist compositions that have very low viscosities as well as compositions that are highly thickened and therefore possess high viscosity. Those with low viscosities are difficult to control and have tendencies to flow away from the target site once they are applied. Compositions with high viscosities are difficult to extrude through a small orifice.
Certain dental compositions may use thickeners such as fumed silica and polyvinyl alcohols. Problems encountered in using these thickeners include aging, which results in non-homogenous gels which make handling difficult, and shear thinning, which reduces the viscosity of a gel when extruded through an orifice and thinning at elevated temperatures. Thinning can result in a material that drips from the orifice and that may fail to remain localized at the desired point of application.
The present invention provides a dental composition suitable for application in the oral environment comprising a thermally responsive viscosity modifier that is capable of undergoing an increase in viscosity in response to an increase in temperature. These compositions also preferably have the ability to reverse their viscosity upon the lowering of temperature.
Compositions of the invention work very well in the oral environment where temperature is generally higher than ambient or the pre-treatment temperature of a composition. This differential in temperature thickens the composition and thus provides a thickened, semi-solid or gel-like composition in the oral environment.
A preferred method of use of the invention comprises applying the composition directly onto the oral surface. Upon exposure of the composition to the oral temperature, the composition thickens to a semi-solid or gel-like state.
In one aspect, the present invention provides a method of applying a dental composition in the oral environment using a dental composition comprising about 10% by weight to about 50% by weight of a thermally responsive viscosity modifier and an adjuvant, wherein the composition is in a low viscosity state at a pre-treatment temperature and a highly viscous state at a treatment temperature that is higher than the pre-treatment temperature. The method includes applying the composition through an orifice, preferably the orifice of a syringe, onto a surface, wherein the composition is at the pretreatment temperature and in the low viscosity state prior to being applied onto the surface, allowing the composition to warm to the treatment temperature and increase in viscosity to the highly viscous state wherein the viscosity of the composition at the treatment temperature is at least about 10 times the viscosity of the composition at the pre-treatment temperature, and allowing the composition to remain on the surface. Preferably the pre-treatment temperature is at most about room temperature and the treatment temperature is about body temperature. Preferred adjuvants include acids, whitening agents, fluoride, anti-microbial agents, and medicaments.